Industrial processes often involve fluid processing to change or refine raw materials to create end products. The process fluids typically include solutions composed of two or more substances. It is desirable to measure concentration of the substances in the solutions at various points within the process. Known industrial process devices determine solution concentration by measuring conductivity of the solution. Disadvantageously, relying on conductivity measurements is problematic when solution conductivity as a function of concentration is not single-valued. In other words, a single measured solution conductivity value may correspond to more than one solution concentration value. As a result, the measured solution conductivity values can be ambiguous as to which concentration value they correspond.